NDT Advance Access originally published online on September 6, 2006
Nephrology Dialysis Transplantation 2006 21(11):3172-3179; doi:10.1093/ndt/gfl366
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Evaluation of histological techniques for quantifying haemodialysis arteriovenous (AV) graft hyperplasia*
1Department of Medicine, 2Department of Pharmacology and Toxicology and 3Department of Pharmaceutics and Pharmaceutical Chemistry, University of Utah and 4Medical Service, Veterans Affairs Salt Lake City Healthcare System, Salt Lake City, UT, USA
Correspondence and offprint requests to: Christi M. Terry, Dialysis Programme, 85 North Medical Dr, East, Rm. 201, Salt Lake City, UT 84112-5350, USA. Email: Christi.terry{at}hsc.utah.edu
Background. Assessing treatment efficacies for preventing haemodialysis arteriovenous (AV) graft stenosis requires a reproducible method for quantifying intimal hyperplasia. We identified sources of variability in three histological methods for assessing hyperplasia in a porcine AV graft model.
Methods. Carotid-jugular synthetic grafts were placed in pigs. After explantation at 3–6 weeks, the tissue was stained with haematoxylin and eosin (H&E), Masson's trichrome or elastic tissue Van Gieson (EVG) stains and examined histologically. Hyperplasia at the anastomosis of 14 grafts was quantified using three different methods, each by four blinded observers. These methods were visual scoring, ratio of intima-to-media surface area (I/M ratio), and ratio of intra-graft hyperplasia to graft surface area (H/G ratio) at the graft–vessel interface.
Results. The EVG stain proved superior in delineation of the elastic lamina yet quantification of the intimal and medial layers was still often difficult. This is illustrated by the greater inter-observer median coefficient of variances (CV) found using the I/M ratio method (intimal area CV = 13.7%; medial area CV = 32.7%; I/M ratio CV = 44.0%) than with the H/G method (intra-graft hyperplasia area CV = 7.3%, graft area CV = 5.3%; H/G ratio CV = 6.9%) or by visual scoring (CV = 26.8%). The H/G ratios correlated positively with visual scores (r = 0.941; P = 0.0007; n = 14) and the I/M ratio (r = 0.719; P = 0.0095; n = 14). While hyperplasia was seen in both native vessel and graft lumen, in only one of the 14 anastomoses was the degree of hyperplasia greater in the native vessel than in the graft lumen, suggesting that the degree of hyperplasia occurring within the graft lumen predicted the total hyperplasia around the anastomosis.
Conclusions. The H/G method for assessing hyperplasia is preferred in a porcine model of AV graft because it is quantitative, less variable and does not require the delineation of the elastic lamina, although it infrequently underestimates the total hyperplasia that occurs.
Keywords: arteriovenous PTFE graft; haemodialysis; hyperplasia; intima–media ratio; methodology; porcine model
* This work was previously presented in abstract form at the American Society of Nephrology Annual Meeting, in Philadelphia, Pennsylvania on November 11, 2005.